Until recently, most wireless communications sites included radio systems located on the ground level in a building, cabinet or other shelter. The direct current (DC) power supply, baseband controller, amplifiers and radios were historically located in one location within the shelter. From this location, coaxial cable was run from the radios to antennas that were supported on a tower outside the building.
Latest generation wireless communications systems, referred to as distributed antenna systems (DAS), distributed DC radio systems, remote radio heads (RRH), 4G and long term evolution (LTE) cellular communication systems, now commonly locate the radios next to the antennas on the tower outside of the communications shelter.
In these next-generation facilities, the baseband system module that controls radio traffic is still located at the ground level shelter, but the radios are separated from the controllers up to several hundred feet and controlled by fiber optic links. The radios are powered directly by DC feeds from the DC power plant that extend up the tower and to the radios. In some cases, the DC cables and fiber optic cables are run separately up the tower and in other cases they are all bundled together in one large hybrid cable.
Optical fiber signal testing often increases connection complexity and the load of installed equipment, such as passive components and fiber patchcords. Optical fiber testing also may increase connectivity failures as correct polarity becomes difficult to control and challenges infrastructure management in the already densely populated communication sites. As a result, telecommunication vendors often avoid implementing monitoring solutions downgrading the quality of the network physical layer infrastructure.